One point of clarification: the C version does not have (and never had) a hash table; the C version had a BST (an AVL tree). Moreover, the "Rust hash table implementation" is in fact still B-tree based; the hash table described in the post is a much more nuanced implementation detail. The hash table implementation has really nothing to do with the C/Rust delta -- which is entirely a BST/B-tree delta. As I described in the post, implementing a B-tree in C is arduous -- and implementing a B-tree in C as a library would be absolutely brutal (because a B-tree relies on moving data). As I said in the piece, the memory safety of Rust is very much affecting performance here: it allows for the much more efficient data structure implementation.